Industrial production of powders involves mechanical forces fracturing individual particles of material into ever-smaller particles. The theory explaining this fracturing recognizes two general types of behavior exhibited by material under stress: elastic and plastic deformation. Elastic deformation occurs when stress is placed or a brittle material, which deforms and then returns to its original shape when stress is removed. If the material is stressed too heavily, however, excess energy builds up and the material fractures. This behavior makes brittle material fracture suddenly when subjected to mechanical impact by powder-making machines. No brittle, or ductile, materials by contrast, are harder to fracture, since they respond to comparable amounts of stress by deforming plastically, that is, by changing sh ape permanently. Excess energy that builds up in the strained material is expended in deformation of the material rather than in fracturing. Plastic behavior can al so be exhibited by brittle materials as their particles become smaller during processing and thus less susceptible to fracturing.
反义词
28. DISAVOW
A. instigate B. acknowledge C. envision D. ameliorate E. inculcate
29. FLOURISH
A. lose out B. catch up C. turn off D. waste away E. slow down
30. HYPERBOLE
A. misdemeanor B. understatement C. imprecation D. concession E. obstinacy
31. RIVETING
A. appetizing B. enriching C. wearisome D. wasteful E. harmful
32. DAMN
A. undo B. entreat C. mollify D. motivate E. extol
33. REPROACH
A. sustain B. advance C. acclaim D. manipulate E. embellish
34. MYOPIA
A. maturity B. prescience C. prompt response D. good fortune E. final event
35. NICE
A. restrained B. colorless C. obscure D. imprecise E. balanced
36. LASSITUDE
A. pride B. breadth C. vim D. pomp E. valor
37. PUSILLANIMOUS
A. successful B. sociable C. adept D. stouthearted E. trustworthy
38. ABASE
A. aggrandize B. limit C. defy D. purify E. destabilize
参考答案：
BDBC ECBD CDA